KR100320083B1 - Improved Automatic Recirculation Valve - Google Patents

Abstract

The automatic recirculation valve 10 has an inlet 16, a main outlet 18, and a recycle outlet 20. The main valve element 28 that reacts to the inflow between the inlet 16 and the main outlet 18 and the bypass element 32 that responds to the inflow of the main valve element 28 to the recycle outlet 20. Adjust fluid inflow. Bypass element 32 includes orifices 52a and 52b that allow fluid to flow to recycle outlet 20. The orifices 52a and 52b are arranged to counteract the fluid pressure acting on the bypass element 32.

Description

Improved automatic recirculation valve

Background of the present invention

The present invention relates to an automatic recirculation valve, in particular a recirculation valve that regulates bypass recycle flow in a centrifugal pump system.

Recirculation valves are commonly used in centrifugal pump applications to prevent pump overheating and maintain hydraulic stability. Pump overheating is due to the transfer of heat energy generated by the pump into the fluid passing through the pump. During normal operating conditions in a properly designed system (required state of normal downstream flow to the pumped fluid), sufficient fluid flow passes through the pump and thus prevents overheating to absorb and transfer the transferred heat. However, during periods when a small amount of flow is required, the temperature of the fluid inside continues to increase as slower moving or stagnant fluid absorbs more heat during residence time in the pump. As the temperature of the fluid in the pump increases, its vapor pressure increases, causing cavitation that can damage the pump impeller and the housing.

Low flow conditions can also result in a phenomenon known as conventional internal recycling. In low flow conditions, hydraulic anomalies can occur in the pump. These hydraulic abnormalities are the response of the fluid to less than optimal pump internal geometry at low flow rates, and generally begin in the region where the fluid discharges the impeller near the pump housing discharge. This phenomenon, known as internal recirculation, causes cavitation that can damage the pump impeller.

The recirculation valve prevents pump overheating and maintains hydraulic stability by providing a second path that allows the pump to maintain a sufficient fluid flow rate for low downstream flow demand periods. A commonly used form of recirculation valve is a modulating flow valve as disclosed in US Pat. No. 4,095,611 and US Pat. No. 4,941,502. These patents disclose valves having an inlet, a main outlet, a recycle outlet, a main inflow element, and a bypass element with a slotted orifice. These valves are located downstream of the pump. Fluid enters the valve from the pump through the inlet and exits the valve through the main outlet to meet downstream demand. The recycle outlet is connected to a second fluid path, such as a low pressure reservoir or a pump inlet that is regulated for a period of time where the fluid requires less flow at the main outlet.

The main valve element responds to the flow rate between the valve inlet and the main outlet. During normal downstream demand periods, the pressure differential across the main valve element opens the valve element to allow flow to the main outlet, while at the same time closing the bypass valve element and preventing fluid inflow to the recycle outlet. Conversely, during a small downstream demand period, the main valve element returns to the closed (sitting) position, thereby opening the bypass element and allowing the inlet to the second path through the recycle outlet. In addition, the main valve element, when seated, serves as a check valve that prevents reverse rotation of the pump impeller when the pump is shut off.

A problem associated with the use of such recirculation valves is that as the bypass element approaches the open or closed position, the unbalanced fluid pressure acting on the bypass element may destabilize the movement of the bypass element. This impairs the recirculation and checking performance of the valve. The bypass valve element includes a slotted orifice on the wall of the hollow shaft, through which the fluid flows from the valve inlet to the recycle outlet through the hollow shaft for a period of time requiring less flow. The orifice is opened and closed by adjusting the hollow shaft relative to a fixed valve member that blocks the orifice in the closed position. It has been found that the fluid pressure acting along the wall of the orifice is not constant, especially when the bypass element approaches the bypass open or closed position. This results in net force acting on the axis which may destabilize the mobility of the bypass element and impair the performance of the recirculation valve.

It is therefore an object of the present invention to provide an improved recirculation valve.

Another object of the present invention is to provide a recirculation valve having a bypass valve element that operates more smoothly.

It is a further object of the present invention to provide a bypass valve element for a recirculation valve that balances the fluid pressure acting on the orifice in order to provide more reliable performance.

Additional objects and novel features of the invention will be set forth on the basis of the following description and the following examples which are to be understood by those skilled in the art or to be understood by the embodiments of the invention. The objects and advantages of the invention are realized and attained by means and combinations particularly pointed out in the appended claims.

Summary of the invention

The present invention provides an improved automatic recirculation valve to protect the centrifugal pump from damage due to overheating or hydraulic fluid instability. The present invention is directed to an inlet, a main outlet, a recycle outlet, a main valve element that reacts to the flow between the inlet and the main outlet, and a reaction to the main valve element to regulate the fluid flow between the inlet and the recycle outlet. And a valve having a bypass element. The bypass element includes first and second orifices that open to allow the recycle fluid to flow. The openings of the two orifices are arranged such that the fluid pressure acting on one orifice opening is offset by the fluid pressure acting on the other opening, thereby providing a smoother operating bypass element that moves uniformly in response to the main flow change. Thereby providing an improved recirculation valve.

The foregoing summary as well as the following detailed description will be better understood with reference to the accompanying drawings. For the purpose of illustrating the invention, it is to be understood that the presently preferred embodiments are shown in the drawings, but the invention is not limited to the precise arrangements and arrangements shown.

1 is a cross-sectional view of the closed position of the main valve element and the fully open position of the bypass element according to the invention.

2 is a partially enlarged view of the bypass shown for some open states.

Referring to the drawings, FIG. 1 shows a regulating recirculation control valve 10 according to the present invention comprising a main body 12 and a bonnet piece 14 attached to the main body 12. The bonnet portion 14 may be attached to the main body 12 by any suitable means, including threaded grooves or threaded connections or bolted connections. The recirculation valve 10 has an inlet 16 connected downstream of the centrifugal pump to receive the pumped fluid and a main outlet for allowing the fluid to flow toward a source of downstream pump demand ( 18) and a recirculation outlet 20 which causes the pumped fluid to be directed to or returned to the low pressure reservoir for a low downstream pump demand period. Although flange connections are shown for the inlet and the two outlets, any suitable pipe connecting means can be used.

The extension between the inlet 16 and the main outlet 18 includes a main passage 22 comprising a lower main passage 24 and an upper main passage 26 divided by a main valve element 28 which will be described later. )to be. The bypass passage 30 extends from the lower passage 24 to the recycle outlet 20 and is separated from the lower main passage by a bypass valve element 32 which will be described later.

A main valve element 28 located within the main passage 22 and moving in response to fluid flow and a fluid flow between the lower main passage 24 and the recirculation passage 30 in response to the movement of the main valve element 28. An internal valve element comprising a bypass element 32 positioned to control the recirculation flow is regulated.

The main valve element 28 contacts the valve seat 40 to seal the main valve element 28 when the circular valve disc 34, the upper surface 36, and the main valve element are in a fully closed position. Sealing surface 38. The seat 40 as shown is formed as part of the main valve body 12, but may also include a separably replaceable seat element.

Bypass valve element 32 comprising cylindrical shaft 42 is attached to main valve element 28 and moves together. The shaft 42 is inserted into the lower main passage 24 along the vertical center axis 44 of the valve 10. The shaft 42 is divided into two, such as the lower shaft chamber 46 and the upper shaft chamber 48, which are separated by the separating element 50 and sealed at the ends by plug grooves 51a and 51b which are threaded or welded. And a hollow chamber. The lower shaft chamber 46 communicates with the lower main passage 24 through the slotted orifice 52a and with the recirculation passage 30 through the circular aperture 54a. Likewise, the upper shaft chamber 48 is in communication with the lower main passage 24 through the circular through hole 54b and is connected with the recirculation passage through the slotted orifice 52b.

Cylindrical shaft guide bushings 56a, 56b attached to the integral body shaft guide 57 support and guide the bypass element 32 to allow vertical movement of the bypass element along the vertical axis 44. The integral body shaft guide 57 formed as part of the body 12 forms an annular central cavity in communication with it as part of the recirculation passage 30.

The vertical movement of the bypass element 32 is controlled by the movement of the main valve element 28 to which the bypass element 32 is attached. The main valve element 28 can move between the fully closed position and the fully open position, in which the sealing surface 38 comes into contact with the valve seat 40 and in the fully open position the upper main passage 26. The upper surface 36 abuts against the lower surface 60 of the bonnet hub 62, which is inserted in and attached to the bonnet portion 14. As shown, the bonnet hub 62 is formed as part of the bonnet portion 14.

A spiral spring 64 connected at one end to the bonnet hub 62 and at the other to the main valve element 28 advances the main valve element 28 to the fully closed position and becomes compressed.

The properties and performance of the valve 10 can be modified to meet the individual needs of each application. The annular valve insert 65 may be added as shown in FIG. 1 to change the space between the valve disc 34 and the inner wall of the valve body 12 through which the fluid flows. This may control the movement of the valve element 28 in relation to the flow rate through the valve element 28. Inserts can be formed according to individual needs and can be made of any suitable material, such as a metal plate. The valve 10 can be made at a separate flow pressure and / or flow rate in the recirculation passage 30 by adding an orifice plate 67 to the recirculation outlet 20.

With the preferred embodiment of the recirculation valve assembly according to the invention described above, its operation is described. Referring to FIG. 1, the inlet 16 is connected to the outlet of the pump, the main outlet 18 is connected to the source of the downstream demand, and the recycle outlet 20 is the inlet of the low pressure reservoir or pump. It is connected to the negative side.

As shown in FIG. 1, the main valve element 28 is closed because there is no downstream demand for fluid entering through the inlet 16. If there is no downstream demand, the fluid pressure in the upper main passage 26 and the lower main passage 24 are the same, so that the fluid pressures on the valve disc 34 cancel each other, and the spring 64 is the main valve element. Allow 28 to be pushed out to the fully closed position. Bypass element 32 moves with main valve element 28 and moves downward toward the fully open position.

In the fully open position, the bypass element 32 permits fluid inflow from the lower main passage 24 into the recycle passage 30, whereby fluid flows into the inlet 16 and the recycle outlet 20 Headed to. Axial chambers 46 and 48 provide two independent paths for recycle inlet. Fluid may enter the lower shaft chamber 46 from the lower main passage 24 through the slotted orifice 52a and exit to the recycle outlet passage 30 through the circular aperture 54a. Alternatively, fluid may enter the upper axial chamber 48 from the lower main passage 24 through the circular through hole 54b and exit to the recycle outlet passage 30 through the slotted orifice 52b. have. Both shaft chamber passages are equally accessible to the fluid coming from the inlet 16.

Based on the need for fluid downstream of the main outlet 18, a pressure difference is formed between the lower passage 24 and the upper passage 26, resulting in net net fluid pressure on the valve disc 34. Create When this fluid pressure exceeds the pressure exerted on the valve disc 34 by the spring 64, the main valve member 28 and the bypass element 32 attached thereto are connected to the main valve member along the axis 44. Move in the direction of the fully open position. Under conditions requiring normal downstream, the resulting net pressure is large enough to move the main valve element 28 to its fully open position, whereby the attached bypass element moves to the fully closed position.

When the bypass element is fully closed (not shown), the slotted orifices 52a and 52b are aligned adjacent to the axial guide bushings 56a and 56b so that the slotted orifices 52a and 52b are completely covered. Fluid inflow through them is blocked.

Between fully open and fully closed, the bypass element 32 is partially open. That is, the slotted orifices 52a, 52b are partially covered by the shaft guide bushings 56a, 56b as shown in FIG. The recycle fluid flows through the bypass element 32, the flow rate of which depends on the area of the slotted orifice not covered by the axial guide bushings 56a, 56b. While the bypass element is in the intermediate position, it has been found that fluid pressure acts on the walls of the slotted orifices 52a, 52b. These pressures can be counteracted to provide steady movement of the main valve element and bypass element, as will be discussed next.

When the bypass element is in the open position (not completely closed), the high pressure fluid in the lower passage 24 flows into the recirculation passage 30 where the fluid pressure is substantially lowered. The pressure drop of the fluid occurs mainly as it flows through the restricted holes, which are defined by the slotted surfaces 52a and 52b when the bypass element 32 is fully open as in FIG. Or if the bypass element 32 is partially open as in FIG. 2, it is formed by a portion of the slotted orifices 52a, 52b not covered by the axial guide bushings 56a, 56b. For convenience of illustration, dashed lines 66a and 66b represent the edges of the shaft guide bushings 52a and 52b, which define the upper end of the restrictive hole when the bypass is partially open.

Referring to FIG. 1, when the bypass element 32 is fully open, a restrictive hole is formed by the bottom wall surface 68a and the top wall surface 70a of the slotted orifice 52a. These wall surfaces are defined by the axial wall thickness 72 and the slotted orifice width 74. The bottom wall surface 68a and the upper wall surface 70a are both exposed to the high pressure fluid on the lower passage side 24 and the low pressure fluid on the shaft chamber 46 side. The pressure acting on the bottom surface 68a is equal in magnitude and opposite in direction to the pressure on the top wall surface 70a. These two pressures cancel each other, so there is no net pressure acting on the bypass element 32 from the orifice.

The slotted orifice 52b operates similarly to the above when the bypass element is fully open. The fluid pressure on the top wall surface 70b offsets the pressure on the bottom surface 68b and consequently there is no net pressure acting on the bypass element 32 from the orifice.

It can be seen that when the bypass element 32 is completely closed, the orifices 52a and 52b are completely covered by the shaft guide bushings 56a and 56b. The bottom and top walls of slotted orifices 52a are equally exposed only for low pressure fluids, while the bottom and top walls of slotted orifices 52b are equally exposed only to high pressure fluids. As in the fully open position, the fluid pressure acting on the wall surface of each orifice is canceled and there is no net pressure acting on the bypass element 32.

However, if the bypass element is partially open, pure pressure may act on each slotted orifice. Referring to FIG. 2, the restrictive hole is defined by the bottom wall 68a of the slotted orifice 52a and the edge 66a of the shaft guide bushing 56a. A pressure drop occurs over these limiting holes. The upper wall 70a of each slotted orifice 52a is affected only by a low pressure fluid that is similar in pressure to the low pressure fluid of the recirculation passage 30, while the bottom wall 68a is a high pressure fluid of the lower passage 24. Mainly affected. This pressure difference appearing between the top wall 70a and the bottom wall 68a results in a net pressure acting on the inner wall of each slotted orifice 52a, lowering the bypass element 32 toward the fully open position. Push it in the direction. If not canceled, the resulting pressure will hinder the desired movement of the bypass element 32.

Means for canceling the pure pressure on the slotted orifice 52a are provided by a second set of slotted orifices 52b that exert pressures of the same magnitude and opposite direction as the pressure acting on the orifice 52a. . As shown in FIG. 2, the restrictive holes are defined by the edge 66b of the shaft guide bushing 56b and the lower end 68b of the slotted orifice 52b, and across them the high pressure shaft chamber 48. Pressure drop to the low pressure recirculation passage 30 occurs. The upper wall 70b is only exposed to the high pressure fluid of the upper chamber 48 which is similar to the pressure of the high pressure fluid of the lower passage 24, while the bottom wall 68b is mainly exposed to the low pressure fluid of the recycle passage 30. . The pressure difference between the walls 70b, 68b is the same as the pressure acting on the orifice 52a but results in a pure pressure acting in the opposite direction to push the bypass element 32 upwards towards the fully closed position and Therefore, the pressure on the orifice 52a is canceled out. In the illustrated embodiment, the same size, the same number of slotted orifices 52b are provided to offset the orifices 52a. However, the actual number of canceling orifices may only be offset by the sum of the total pure pressures acting on the groups of slotted orifices in one direction by the sum of the pure pressures acting on different groups of slotted orifices in the other direction. It does not have to be equal. This offset in pressure acting on the slotted orifice allows the bypass element to move stably as designed.

The present embodiment can also counteract any fluid pressure acting on the separating member 50 and the plug 51a, which can make the movement of the main valve element 28 unstable. The pure pressure resulting from the high pressure of the lower passage 24 acting on the outer plug surface 76 and the low fluid pressure of the chamber 46 acting on the inner plug surface 78 causes the plug 51a to be in the fully open position. Push it out. This pushes the valve element 28 to the fully closed position due to the high pressure of the upper chamber 48 acting on the separator surface 80 and the low pressure of the lower chamber 46 acting on the separator surface 82. Offset by pure pressure.

As mentioned above, although specific embodiments of the present invention have been disclosed, the present invention is not limited by the above disclosure, and changes and modifications may be made or implemented within the scope of the following claims.

Claims (13)

Inlet; Main outlet; Recycle outlet; A main valve element responsive to flow between the inlet and the main outlet; A bypass valve element responsive to the movement of the main valve element for regulating fluid flow between the inlet and the recycle outlet and including an orifice hole; And Means for canceling fluid pressure acting on the orifice aperture, wherein the offset means comprises a second orifice aperture within the bypass valve element. The method of claim 1, The bypass valve element comprises two hollow chambers, The first orifice aperture permits flow with a first hollow chamber of the two hollow chambers, and the second orifice aperture is positioned to permit flow with a second hollow chamber of the two hollow chambers. . 3. The automatic recirculation valve of claim 2, further comprising an insert for controlling the space through which fluid flows between the main valve element and a valve wall located adjacent the main valve element. 3. The automatic recirculation valve of claim 2, further comprising an orifice plate through which the recirculation fluid flows. 2. The automatic recirculation valve of claim 1, further comprising an insert for controlling the space through which fluid flows between the main valve element and a valve wall located adjacent the main valve element. The automatic recirculation valve of claim 1, further comprising an orifice plate through which the recirculation fluid flows. 2. The automatic recirculation valve of claim 1, further comprising an insert for controlling the space through which fluid flows between the main valve element and a valve wall disposed adjacent the main valve element. 2. The bypass valve element of claim 1, wherein the bypass valve element comprises first and second hollow chambers, wherein the first orifice hole is positioned to allow fluid flow through the first hollow chamber, and the second orifice hole Is a recirculation valve positioned to allow fluid flow through the second hollow chamber. A bypass valve element for controlling the recirculation flow of an automatic recirculation valve having an inlet, a main outlet, a recycle outlet, and a main valve element responsive to the flow between the inlet and the main outlet, Axis; A first hollow chamber inside the shaft; And A first and second orifice aperture allowing fluid flow through the chamber between the inlet and the recycle outlet, wherein the first orifice aperture cancels the fluid pressure acting on the second orifice aperture. Pass valve element. The method of claim 9, Further comprising a second hollow chamber inside the shaft, The first orifice hole permits flow with the first hollow chamber and the second orifice hole permits flow with the second hollow chamber. Inlet; Main outlet; Recycle outlet; A main valve element responsive to flow between the inlet and the main outlet; And A bypass element responsive to said main valve element for regulating flow between said inlet and said recycle outlet, The bypass element, A shaft having first and second hollow chambers, A first orifice hole in the first chamber to allow flow between the inlet and the first chamber, and A second orifice hole in the second chamber that allows fluid connection between the second chamber and the recycle outlet, wherein a fluid pressure acting on the second orifice hole acts on the first orifice hole Improved automatic recirculation valve for fluid pressure cancellation. 12. The improved automatic recirculation valve of claim 11, further comprising an orifice plate through which the recirculation fluid flows. 12. The improved automatic recirculation valve of claim 11, further comprising a valve body integral with said inlet, said main outlet, and said recirculation outlet.